The Constitution prescribes that the Senate be composed of two senators from each State (therefore, the Senate currently has 100 Members) and that a senator must be at least thirty years of age, have been a citizen of the United States for nine years, and, when elected, be a resident of the State from which he or she is chosen. A senator's term of office is six years and approximately one-third of the total membership of the Senate is elected every two years.
Look up brief biographies of Senators from 1774 to the present in the Biographical Directory of the United States Congress. You can find out other facts about Senators past and present and get an overview of the members of Congress using these links.
Membership of the 116th Congress: A Profile (CRS) (pdf)
Congressional Salaries and Allowances (CRS) (pdf)
Retirement Benefits for Members of Congress (CRS) (pdf)
Bibliography on Books by Sitting Senators
Association of Former Members of Congress Web Page (usafmc.org)